The present invention is directed to a method for high throughput screening of potential reactants, catalysts and associated process conditions. The invention is particularly advantageous for use as a method for fluorescent screening of potential reactants and catalysts in solid melt polymerization.
Since its introduction in 1970, combinatorial chemistry has become a popular research tool among scientists in many fields. Combinatorial screening has been prevalent in the pharmaceutical industry for nearly twenty years and, more recently, combinatorial screening for improved catalysts for the bulk chemical industries has enjoyed increasing popularity.
There has been, however, a lag in the development of combinatorial screening for production scale reactions. Rapid combinatorial screening of reactants, catalysts, and associated process conditions requires that a large number of reactions or catalytic systems be tested simultaneously, while still providing a meaningful correlation between test results and eventual performance in a production-scale reactor. Before the application of the combinatorial approach, catalyst testing was traditionally accomplished in bench scale or larger pilot plants in which feed to a continuous flow reactor was contacted with a catalyst under near steady-state reaction conditions. This type of test system can be difficult to reproduce at the micro-scale required for combinatorial chemistry.
Another difficulty is that for many reactions, efficient methods of product analysis have yet to be developed. For example, solid melt polymerization is typically evaluated by determining the amount of high molecular weight polymer formed. Additionally, under some conditions, polymerization is correlated to the amount of Fries rearrangement products formed. Fries rearrangement products result from the conversion of phenolic esters into corresponding ortho and para hydroxyketones as a result of the inherent stability of polybenzenoid compounds. Although the formation of Fries rearrangement products is generally indicative of successful catalysis, the formation of Fries products may reduce the overall efficiency of the reaction by utilizing reaction components required for polymerization.
Traditional techniques for measuring the molecular weight of polymers, such as size-exclusion chromatography and light scattering, require extensive and time-consuming sample preparation steps to dissolve the polymer for analysis. Similar time-consuming sample preparation is also needed for measurement of Fries rearrangement products by traditional techniques such as nuclear magnetic resonance (NMR) and high pressure liquid chromatography (HPLC). Each of these techniques are invasive and ultimately require destruction of the sample.
As the demand for bulk chemicals has continued to grow, new and improved methods of producing more product with existing resources are needed to supply the market. However, the identities of additional effective reactants and catalyst systems for these processes continue to elude the industry. What are needed are new and improved methods and devices suitable for rapid screening of potential reactants, catalysts, and associated process conditions.
The present invention is directed to methods for the rapid, non-destructive screening of potential reactants and catalysts in polymerization reactions. In one aspect, the method of the present invention comprises the steps of irradiating polymerization samples with light of a defined excitation wavelength; monitoring fluorescence emitted from each of the samples; comparing the fluorescence emission from each sample to the fluorescence emission for a database of reactions which have been characterized with respect to a predetermined set of reaction parameters; and correlating the sample fluorescence with selected reaction parameters of interest. Also included in the present invention are systems for performing the method.